Drs. Davis, Fox, and DuBois completed the project on water immersion in dogs. The early diuresis which occurred in compensated immersion (breathing assisted by positive pressure) resulted in a correction of the lowered osmotic pressure, suggesting that osmoreceptors were responsible for the initial phase of the diuresis. Drs. DuBois, Kakiuchi, and Gorenberg began a study of mixed venous oxygen tension, because this tension affects the tissue oxygen tension. Dogs were anesthetized with chloralose and were exposed to air, 5% CO2, air hyperventilation, and air. Arterial and venous PO2, PCO2, and pH were measured. Cardiac output, oxygen consumption, and CO2 output were followed. Breathing 5% CO2 produced a 10 mm Hg increase of mixed venous oxygen tension. About 20% of this rise could be attributed to an increase of cardiac output, and the remainder to the Bohr shift, since the blood was more acid. With hyperventilation, a 9 mm Hg fall below normal venous PO2 occurred. Again, most of this was due to the Bohr shift during alkalosis.